Upper computer range setting for flow rate
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The last edit to this post was made by libra2008 on 2012-12-19 at 10:41. There is a flow meter using an orifice plate to measure steam flow; the flow range specified to the orifice plate manufacturer is 60–200 t/H. After calculating the differential pressure, the manufacturer determined that the upper limit of this range is 25 KPa, with a selected differential pressure range of 0–25 kPa. So what is the measurement range I should set on the DCS? Is it 60~200t/H? Still 0~200t/H? I’m not quite sure; please clarify
For 0~200 t/h, 60 t is the minimum flow rate that can be measured using an orifice plate; measurements taken below 30% of the range with an orifice plate are inaccurate
0-200 :o, 60-200 means that if the value is less than 60, the measurement is not very accurate: hug:
What is typically the range ratio for such orifice plates? Does the measurement become inaccurate when this ratio is exceeded? For example, if my required measurement range is 2.5~25 t/H, then are the readings inaccurate for values below 7.5 t/H?
The flow rate measured by differential pressure flow meters is usually inaccurate below 30%, that is, it is inaccurate below 60 T/h; therefore, small-signal rejection is applied. However, at the initial stage of using the instrument, do not set the small-signal rejection value too high, otherwise the reading will remain at zero. After normal operation, increase the small-signal rejection value； With the orifice plate remaining unchanged, proportional scaling can be used for conversion. If taking the square root into account, the flow rate is linearly related to the pressure difference; setting the lower limit of the transmitter’s range to 7.5 KPa results in a DCS flow rate of 60–200 t/H. If the square root is not considered, the flow rate is related to the pressure difference in a square-root manner; setting the lower limit of the transmitter’s range to 2.25 KPa also yields a DCS flow rate of 60–200 t/H
The settings on the host computer are all values ranging from 0 to 200; the manufacturer specifies that the flow rate should be within this range, and no measurement is necessary if it is below 60. Generally, the formulas for calculating orifice plates are provided by the manufacturers, but they are all based on the national standards for orifice plate flowmeters. As we all know, an orifice plate is a type of differential pressure flow meter. The most common parameters used in calculations include the diameter of the orifice plate, the molecular content and density of the fluid, as well as temperature and pressure compensation, among others. These values are generally constant, with only one variable remaining, which is what we call the differential pressure. When calculating flow rate using an orifice plate, we do so by taking the square root of the differential pressure. In the situation you described, both the range of flow rate and the range of differential pressure start at 0; however, when calculating the flow rate, values of differential pressure that are too low are excluded, resulting in no flow rate values being displayed below 60. Values start to be shown once they reach 60. So in any case, it starts from 0. As for why you need to make so many cuts, I have no idea; you should have chosen a orifice plate with a smaller aperture when making the initial selection!
Thank you to all for their answers. What is the typical range ratio for orifice plates?
There are many forms of differential pressure, and the range ratios for different forms vary; they are usually 5:1, 10:1, 20:1, or even higher
Thank you for your reply. Could you please provide some information on the measurement range of differential pressure? I’m still quite confused about which differential pressure flow meters to choose